Passenger seats of aircrafts that fly long distances are equipped with a bed mode. Many of such passenger seats are made flat by reclining the seat further, but since the seats are equipped with cushions designed to realize comfortable seating, there was a drawback in that that seats could not be made completely flat.
Therefore, the following patent literatures disclose a mechanism of tilting a seat back, which is a backrest of the seat, forward to change the seat into a bed.